Biosynthesis of aspyrone, a metabolite of Aspergillus malleus. Incorporation studies with 14C- and 3H-labelled acetates and malonate
Abstract
Incorporation studies with 14C-labelled acetates and malonate confirm the polyketide origin of aspyrone (1), and identify the chain starter unit. Five carbons are derived from the methyl group of acetate, and the remaining four from the carboxy group. The pattern of incorporation of tritium from [2-3H]acetate is inconsistent with a biosynthesis from aromatic precursors of the mellein type. Possibly advanced precursors containing a 2-methylchromone nucleus were not incorporated. The evidence suggests that aromatic precursors are not involved in aspyrone biosynthesis, and that the carbon skeleton is produced, like that of the co-metabolite asperlactone (6), by decarboxylation and rearrangement of a linear penta-ketide intermediate.